The present invention relates to a projection-type image display apparatus, for modulating light intensity of lights irradiated from an illumination optic system, through liquid crystal image display elements (i.e., panels) for use of lights of R, G and B, in particular, applying polarization effect therein, thereby forming an optic image, and projecting said optic image upon a screen through a projection optic system.
Conventionally, the projection-type image display apparatus was already known by a name, such as, a liquid crystal projector or the like, for example, i.e., containing an optical unit, as well as, an electric source circuit and/or a video driver circuit within a housing thereof, for projecting the optic image that is formed through modulating the light intensity upon the lights from a light source, with applying polarization effect thereto, so as to vary the density for each of pixels, depending on an image signal through light valve elements for use of R-, G- and B-lights, and thereby projecting the said optic image formed onto the screen or the like, by means of a projection lens. Further, at present, as such the light valve element mentioned above is also widely known and practically used, for example, so-called a transmission or a transparent-type liquid crystal panel, or a reflection-type liquid crystal panel, etc.
As the optic unit of such the projection-type image display apparatus is also already known an optic unit, as is disclosed in Japanese Patent Laying-Open No. 2004-126496 (2004) or Japanese Patent Laying-Open No. 2004-184889 (2004), for example, wherein the optic image is formed through cross dichroic prisms, functioning as a color synthesizing element, after conducting the light-intensity modulation on the lights, which are divided with applying the polarization functions, by means of the reflection-type liquid crystal panels for use of the R-, G- and B-lights, and thereby projecting the optical image formed onto the screen or the like, through the projection lens.
Also, an optical unit is already known, in Japanese Patent Laying-Open No. 2005-12303 (2005), for example, (in particular, in the second embodiment shown in FIGS. 3 and 4) wherein the optic image is formed also through the cross dichroic prisms, as the color synthesizing element, but conducting the light intensity modulations of R, G and B lights, with applying the transparent-type liquid crystal panels (or, the transparent-type light valves) therein, in the place of such the reflection-type liquid crystal panels as mentioned above, and thereby projecting the optic image formed onto the screen or the like, through the projection lens.
Also further is already known a cooling structures within the optic unit of projecting the optic image on the screen or the like, which is formed through the cross dichroic prisms while conducting the light intensity modulations of R, G and B lights with applying the reflection-type liquid crystal panels (or, the reflection-type light valves) or the transparent-type liquid crystal panels (or, the transparent-type light valves) therein.